(Reuters) – Chris McDaniel, who lost Mississippi’s Republican U.S. Senate primary last week, on Wednesday blamed his defeat on illegal voting by Democrats and asked supporters for money to mount a legal challenge to the runoff election results.

McDaniel, a state senator backed by the Tea Party, said in an email to supporters that his loss to U.S. Senator Thad Cochran last week was caused by a large number of ineligible Democrats who voted for the six-term incumbent Cochran.

He said the Democrats in question voted in the Democratic primary and then in the Republican runoff, which is against election rules.

“Thanks to illegal voting from liberal Democrats, my opponent stole last week’s runoff election, but I’m not going down without a fight,” McDaniel said in the fundraising email one day after his supporters filed suit to gain access to voter records.

Many of Mississippi’s Democrats are black. The Cochran campaign, which courted black Democrats ahead of the runoff to broaden its base, dismissed McDaniel’s assertions as unfounded.

“His accusations are wild, baseless and irresponsible,” said Jordan Russell, spokesman for the Cochran campaign. “He lost the election. He needs to get over it.”

Under state law, registered voters are free to cast a ballot in a runoff to determine a party’s general election candidate if they did not vote in the other party’s primary.

McDaniel and his supporters allege that thousands of ballots appear to have been cast improperly in the June 24 runoff, many of them by people who voted in the Democratic primary earlier last month. McDaniel lost by roughly 7,000 votes.

In a lawsuit filed Tuesday in federal court in Oxford, Mississippi, True the Vote, a conservative election-monitoring group, together with 13 Mississippi voters sued the state’s Republican party and secretary of state, alleging they refused to turn over voter rolls in two counties.

State Republican party Chairman Joe Nosef said in a statement that the lawsuit was misguided and that his party would seek to remove itself as a defendant.

A Secretary of State spokeswoman referred queries to the state Attorney General’s office, which did not immediately respond to requests for comment.

(Reporting by Jonathan Kaminsky in New Orleans; Editing by Cynthia Osterman and Lisa Shumaker)